1. Field of the Invention
The present invention relates to buildings. More specifically, the present invention relates to a panel assembly usable as residential load bearing roof decking that reflects solar thermal energy back into the atmosphere as well as reflecting internal thermal radiation back into the structure when retention of warm temperature is desired.
2. Description of the Related Art
Approximately eighty-five percent of heat energy entering a structure is due to solar radiation. Initially, absorption occurs at the Earth's atmosphere and then by striking the Earth. Objects on Earth then transfer the reduced heat energy through conduction or convection.
With respect to roof-top sheathing materials, the heated exterior surface of the roof conducts heat to interior surfaces. The rate of transfer, known as the R-factor, depends on the thickness and density of each individual material through which the radiation must pass.
In addition, interior chambers of a structure (e.g., an attic or living compartment) receive radiation from the inside surfaces of exterior material to inside air. This process sets up a convection cycle causing heat to transfer to the interior of the structure.
One approach to addressing the problem of heating from absorption is by lining the inner surface of the roof with a radiant barrier designed to reflect the energy. For example, Norbord Inc. of Canada manufactures a radiant barrier sheathing under the trade name SOLARBORD that is a combination of a heat-reflecting foil laminated to oriented strand board (OSB). Norbord reports that its radiant barrier sheathing reduces attic temperatures by up to thirty degrees (F.) and reduces radiant heat transfer through the roof by ninety-seven percent. See www.solarbordosb.com.
In addition to sheathing, properties of various materials and air may be combined to effectively reduce radiation transfer to the interior of a structure. Specifically, because still air, or “dead air,” cannot directly conduct heat, convection must occur for heat transfer to take place. In other words, by reducing convection, heat transfer is also reduced. Radiation, however, passes through still air regardless of presence or absence of convection currents.